1. Field of the Invention
The present invention relates to semiconductor device manufacturing equipment, and more particularly to an apparatus and method for testing an inker used in a semiconductor wafer probe station.
2. Backgound of the Invention
At the end of a semiconductor fabrication process, there is normally performed a series of wafer test processes in order to sort good and failed chips of the wafer through testing of electrical characteristics in each chip. Such a wafer test process is also called "Electrical Die Sorting (EDS)" in DRAM fabrication area. Upon completion of the die testing, failed chips are marked with an ink to identify them with the naked eye in a subsequent assembly process. This inking process is performed by an inker provided in the wafer probe station.
A conventional inker device is shown in FIG. 1. The inker 10 includes an ink reservoir 14 and ink tube 15 through which an inkline 18 is inserted. The upper end of inkline 18 is coupled to a shaft 13 which is in turn coupled to the plunger of a solenoid 12. The ink reservoir 14 and solenoid 12 are mounted to an arm 22 so that the inkline 18 and shaft 13 are aligned with the solenoid plunger and moved up and down a short distance by actuation of the solenoid 12. The inker mounting arm 22 is extended to a support member 86 via an extension bar and coupled by a hinge pin 25. Provided at upper portion of the extension bar are a thumb screw 24 for XY preload adjustment, an XY positioning lever 26, a Z-adjust thumb screw 27, and a nylon ball 28 for preloading an amount of weight onto the hinged inker mounting arm 22. Also, reference numeral 16 denotes a screw for holding inkline fine adjustment knob. The wafer 42 is mounted onto a vacuum chuck 40 and located beneath the inker 10.
Details of the inker reservoir 14 and inkline 18 are shown in FIG. 2, in which inkline 18 is extended outside the ink tube 15 and the inker 10 has been adjusted to locate the extended inkline 18' above the wafer 42, approximately 2 mils away from the wafer surface. The ink 16 contained in the reservoir 14 migrates to the tip of the inkline 18' through the gap between the ink tube 15 and inkline 18. Although the inkline 18' is out of contact with the wafer surface 42, ink transfer can be made by the principle of "surface tension."
The inkline 18 is also moved between the retraction and protrusion position by the movement of the shaft 13 coupled to the plunger of the solenoid 12. The distance of the inkline retraction, denoted by D1, is about 30 mils. Also, the distance of the inkline protrusion, denoted by D2, is about 30 mils. The distance of the inkline travel Dt will be about 60 mils. Reference numeral Dw denotes the distance of inkline to the wafer surface when inkline is extended.
It is essential that the inkline 18 is moved to the desired protrusion position and the distance of the inkline protrusion is maintained during the inking process. Thus, it is necessary to test the inker device before starting the inking process. The inker test has been performed such that an inker test button provided in the probe station is pressed to produce test signals which are supplied to an inker solenoid and then the solenoid movement is observed by the operator. Secondly, the inker test is carried out at the side part of a wafer to identify operation of the inkline by observing the ink mark on the wafer.
The prior art inker test method, however, is troublesome and time-consuming since each test step is performed manually by an operator. Further, the number of inker test operations and the test speed may vary depending on each operator, with the result that errors occur during every test and the test operations are not reliable. Furthermore, since observations are made by the naked eye, only malfunctions capable of detection by the naked eye can be detected. Another problem experienced in known probe stations is that the number of inker test operations and the operating time cannot be set up to depend on the kind of inker being used. This results in a difficulty in testing all kinds of inkers accurately and thus, lowers the quality of inker testing.